1. Field of the Invention
The present invention relates to an electronic paper display apparatus and a method thereof; and more particularly, to an electronic paper display apparatus and a method thereof in which the rotational property of rotating balls is improved.
2. Description of the Related Art
Among next-generation display apparatuses, an electronic paper display apparatus has been known have good availability and flexibility properties as against another display apparatuses, and operate at a low-power. As such, the electronic paper display apparatus may be substituted for a paper sheet printing medium such as a book form. Further, the electronic paper display apparatus may be most widely applicable to various types of display screen or electronic wallpaper.
Recently, one of the leading electronic paper display apparatuses is a twist ball type. of electronic paper display apparatus which uses plural pairs of rotating balls, each pair having two hemispheres of different colors. Such a twist ball type of electronic paper display apparatus includes the plurality of rotating balls, a partition wall member which separates the plurality of rotating balls from each other, an electrode structure which rotates the plurality of rotating balls, and a transparent insulating oil which provides a lubricating property to the plurality of rotating balls.
In the electronic paper display apparatus with a configuration as described above, the plurality of rotating balls are selectively operated to produce a color, which requires the rotating balls having a high rotational property. Factors that influence the property of the rotating balls may include an actual rotational property value of rotating balls, a type of insulating oil, a distance between partition wall members which transversely separate the rotating balls from each other, a distance between lower and upper structures which vertically house the rotating balls, or the like. Among these, distances between the rotating balls and each of the lower and upper structures may drastically influence the rotational property of the rotating balls. The reason for this is that the rotating balls vertically move during the rotation operation thereof. As such, when the distances between the rotating balls and each of the lower and upper structures falls outside a predetermined range, the rotational property of the rotating balls is drastically deteriorated.
In recent years, there is a technique which disposing plural pairs of rotating balls each pair having different sizes on the same plane. For example, in the each pair of rotating balls, one having a relatively larger size requires a relatively high level of drive voltage compared to the other. Using the difference in the drive voltages between the pair of rotating balls, the electrode structure adjusts the potential of the drive voltage on a step-by-step manner, thereby selectively rotating the rotating balls having different sizes, which in turn, controls the gradation of the electronic paper display apparatus on a step-by-step manner. Unfortunately, when the plural pairs of rotating balls each pair having different sizes are disposed on the same plane, the distances between the rotating balls and each of the lower and upper structures may be varied depending on the size of the rotating balls, which causes a non-uniform rotational property.